LED, LEDs are widely used in vehicles, for example, as an interior lamp in a compartment of a vehicle. However, luminance of LEDs is often not uniform, and a bright lamp-emitting area is often not large enough, for example, within 30 mm. Even the lamp having a wide cross-section of a lamp door, except the bright lamp-emitting area, other areas may not be bright enough.
Because of the uneven luminance of the LEDs, the illuminated area of the compartment may not be large enough, and the efficiency of the LED lamp may be low.